1. Field of the Invention
This invention relates generally to a technique for mounting a stack of stator core plates to construction bolts associated with an inner frame of a high power generator and, more particularly, to a technique for mounting stator plate packs to construction bolts associated with an inner frame of a high voltage generator, where the technique employs a single wedge set positioned within each mounting slot in the stator pack and provided on one side of each construction bolt positioned within the slot.
2. Discussion of the Related Art
High voltage generators for generating electricity as a power source are well known in the art. A power plant may include a gas turbine engine that rotates a shaft by combusting fuel and air in a combustion chamber to generate a working fluid that expands across blades that rotate, and in turn causes the shaft to rotate. The shaft of such an engine is coupled to an input shaft of a high voltage generator that is mounted to a rotor having a special configuration of coils. An electrical current provided in the rotor coils generates a magnetic flux around the coils, and as the rotor rotates, the magnetic flux interacts with windings in a stator core enclosing the rotor. The stator core windings may include interconnected stator bars that have a special configuration to reduce eddy currents in the core, which would otherwise generate significant heat and possibly damage various generator components.
A stator core for a high voltage generator is typically a stacked assembly of several thousand laminations of a relatively thin ferrous material, such as iron or steel. Each lamination is formed by configuring a plurality of pie-shaped plate sections, such as nine sections, to form a laminate plate ring, where each section is stamped from a piece of the ferrous material. A number of these laminate plate rings are then stacked on top of each of other within a fixture where they are compressed together. The compressed stack of laminate plate rings are placed in a vacuum chamber where a resin is used to secure the rings together and where the resin is cured in a heated oven. The resulting stack of plate rings forms a single unit often referred to as a stator pack or donut. The stator packs are then assembled together to form the stator core in a generator frame by sliding each stator pack onto a plurality of construction or building bolts circumferentially disposed around an inner bore of the frame. Once all of the stator packs are mounted within the generator frame, a series of through-bolts extend through aligned openings in the stator pack which are used to compress the stator packs together to form the final stator core. U.S. Pat. No. 5,875,540 issued to Sargeant et al., assigned to the assignee of this invention and herein incorporated by reference, provides a more detailed discussion of the stator core assembly process discussed above.
In one stator core assembly operation, the stator packs are slid onto the construction bolts and supported by a series of notches circumferentially disposed around the stator packs, where a plurality of stator packs, such as four or five stator packs, are secured to the construction bolts using opposing wedge sets on each side of the construction bolt. Each wedge set includes opposing outer filler members and an internal wedge member where the wedge member is forced between the filler members to securely hold the stator pack to the construction bolts. A typical stator core may have eighteen construction bolts, thus requiring thirty six wedge sets to secure the group of four or five stator packs to the construction bolts during assembly, where the stator core may include 30-35 stator packs and have a length of about 200 inches.
The process of assembling the stator core of a high voltage generator is sometimes performed at the final installation site of the generator because of the assembled size of the stator core. Assembly of the generator at the final installation site requires tight scheduling controls and procedures as a result of the size of the generator and the space requirements necessary. Positioning thirty-six wedge sets for each group of the stator packs, where several groups of the stator packs make up the stator core, is labor intensive and requires significant time. Any unforeseen delays or other issues during assembly of the stator core affects the entire assembly schedule, which has significant effects on cost.